Source: Chemistry World | Kit Chapman | March 16, 2018
As Oak Ridge National Laboratory celebrates its 75th anniversary, Kit Chapman visits the birthplace of the atomic age.
In October 1942, the farmers working in the quiet valley west of Knoxville, US, came back from tending their fields to find notices on their doors. The US Army had visited every homestead along a 17-mile stretch of the Clinch river, passing along the winding dirt roads that cut through the woodland at the edge of the Great Smoky Mountains. The notices told the residents they had six weeks to leave their land forever. The second world war had come to Tennessee.
The site had been handpicked for a military base by Brigadier General Leslie Groves, the officer in charge of the secret Manhattan Project. He chose the valley for several reasons: it was remote, but had good road and rail links, and during the Great Depression massive hydroelectric dams had been built in the area, providing a secure source of electricity. Just as importantly, the valley had several natural ridge lines, shielding each part of the operation from the other. That kind of natural barrier mattered when you were building an atomic bomb.
By autumn 1943, the army had taken full control of the valley, transforming it on a scale never seen before or since. Within two years, a thriving community had emerged behind the fence, home to 75,000 people – scientists, soldiers and their families. They even had future celebrities scattered among them; one of the assistant cafeteria managers, Harland Sanders, would go on to found Kentucky Fried Chicken. Save for a regular convoy of army trucks, nobody went in and nobody went out.
Most of the workers did not understand their secret task, but the scale of the operation told them how much it mattered. In one valley sat the largest building in the world, the K-25 gaseous diffusion plant, its 152,000m2 of floor space dedicated to enriching uranium. In another was Y-12, home to the Manhattan Project’s calutrons, large magnets on a racetrack for separating uranium isotopes. Finally, in a humble building of corrugated iron that looked like an old steel mill, there was X-10. Inside, Italian-American physicist and Enrico Fermi was present when the world’s first permanent nuclear reactor went critical, bathing uranium rods with slow neutrons to convert it first into neptunium, then into the first gram quantities of plutonium that would inform the design of the first atomic bomb.
The secret city needed a name, something that wouldn’t raise any eyebrows if overheard by foreign agents. In the end, the Army settled on Oak Ridge. 75 years later, Chemistry World paid them a visit.
From war to peace
Today, Oak Ridge National Laboratory (ORNL) is the largest science and energy lab in the Department of Energy’s national lab system. In the 75 years since its inception, ORNL has remained a powerhouse of scientific achievement in the US. Y-12, now a separate facility, remains just across the ridge, still a national security complex; the X-10 reactor remains too, powered down and preserved as a monument to the birth of nuclear power.
‘At the end of the war we had the best neutron source in the world,’ explains James Roberto, who retired as associate laboratory director in December 2017. ‘Eugene Wigner [the Nobel prize-winning physicist and the lab’s director of R&D from 1946] had a vision. Why not build a national laboratory around it? The US was in the process of trying to build a commercial nuclear power industry, and needed a reactor that could be used for fuels and separation chemistry.’ Nobody outside the Manhattan Project knew about nuclear reactors – so Oak Ridge helped develop nuclear engineering, teaching thousands of new nuclear engineers and even helping the US Navy develop its nuclear fleet.